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THE INVASION OF SAURIDA 

ABSTRACT: The Red Sea lizardfish, Saurida undosquamis(Richardson), invaded the Levant Basin and established a population of considerable commercial importance. Its expansion came at the expense of other commercial fishes on which it preys and with which it competes. The explosion ofthe Red Sea lizardfish population in the Levant Basin was made possible by a combination of changes in the environmental conditions (abiotic and biotic), one of these being the retreat of, or the recession in, the native hake population. The dynamic coexistence between the lizardfish and the hake, its main competitor, is affected by fluctuations in the abiotic conditions to which the hake seems to be more sensitive than the lizardfish. A faunistic, zoogeographical approach to the marine animal migration through the Suez Canal is common to most investigators of the canal's influence. Animal species native to one sea and found in the other after the opening of the canal serve as main indicators ofits biological influence and of its effectivity as a link to the migrant species and as a barrier to others (Ben-Tuvia, 1966, in press; Kimor, 19703 ; Por, 1971; Steinitz, H., 1968; Steinitz, W., 1929; Thorson, 1971). Many ), suggesting that the mechanism of the penetration of some species through the canal and their expansion in the Mediterranean is associated with environmental conditions (salinity, currents, nature ofsubstrate, etc,). In this paper we discuss the ecology of the mi­ gration and expansion in the new habitat of an important commercial fish. We examine its dynamic coexistence with its native competitor in view of the changing environmental conditions.